Stroke victims or others who have lost the ability to speak clearly through accident or surgery, for example, often undergo long hours of speech therapy that requires the patient to match or imitate their spoken words with a word or phrase that they hear. Because speech sounds different to the person who is speaking than it does to others who are hearing that person, it is frequently difficult for someone to accurately hear what they are saying when attempting to imitate words and phrases. Students learning to sing also have trouble mastering proper vocal techniques due to this difference in sound perception between the student and teacher. People who are deaf or have lost their hearing have an even more difficult time in either learning to speak or to continue to speak clearly enough to be understood. Without the ability to hear what is being spoken, an individual has no way to tell what their words sound like, and hence no way to tell how to speak more clearly, or even how to speak at all. Methods are needed which improve the efficiency and quality of speech therapy and vocal instruction.